The present invention is drawn to a system for improving the production of crude oil by the injection of treatment fluids into the pumping chamber of a subsurface oil pump and, more particularly, a system for securing the pump within the production tube of the well thereby allowing a pump barrel with the metering valve for introducing treatment fluids into the pump chamber to be removed from the production tube as a unit.
It is a further feature of the present invention to provide an inlet valve-metering valve assembly which is adapted to be used with various sized pump barrel-pump piston assemblies. There are various methods known in the prior art for injecting treatment fluids into a production well. The term treatment fluids embraces all types of fluids which might be employed including viscosity reducing fluids, maintenance fluids, corrosion inhibitor fluids and the like.
FIG. 1 depicts a typical production system known in the prior art for introducing treatment fluids into a well In accordance with the system illustrated in FIG. 1, an injection of the treatment fluid takes place in an annular space defined between the well casing and the production tube. Mixing of the crude oil in the treatment fluids occurs in an area below the intake valve of the subsurface oil pump. This procedure has been found to be unsatisfactory due to the fact that hydrostatic pressure is exerted by the column of treatment fluid injected into the well on the underground reservoir. This pressure exerted on the underground reservoir diminishes the rate at which crude oil from the underground formation enters the well thereby decreasing the efficiency of oil production.
A further system known in the prior art for injecting treatment fluids into an underground reservoir is illustrated in FIG. 2. In the particular arrangement shown in FIG. 2, the treatment fluid is injected down the production tube and the mixing of the treatment fluid and oil occurs within a perforated nipple located some distance above the subsurface oil pump. The treatment fluids-oil mixture flows to the surface of the well via perforations in the nipple wherein the mixture is transferred to the annular space defined by the well casing in the production tube. There are two major disadvantages associated with the foregoing arrangement. One disadvantage results from the fact that the treatment fluid does not pass through the production subsurface oil pump when injected in this manner. As a result, the high viscosity of the crude oil can cause deterioration of the pump components and ultimate failure of the pump. In addition, in the arrangement shown in FIG. 2, it is impossible to introduce anti-corrosive treatment fluids to protect the pump components. A further disadvantage results from the fact that it is extremely difficult to control with precision the amount of treatment fluid admixed with the oil.
A known method for the controlled introduction of treatment fluids into a well is disclosed in U.S. Pat. No. 4,791,985 and is schematically illustrated in FIG. 3. The system disclosed in the '985 patent overcomes many of the disadvantages noted above with regard to other known prior art systems. As can be seen in FIG. 3, the system includes a subsurface oil pump which communicates with the annular space defined between the production tube and the well casing for introducing treatment fluids into the pump chamber. A metering valve is provided for controlling the flow of treatment fluid into the pump chamber thereby allowing for the precise control of the quantity of treatment fluid being introduced. Thus, the prior art system shown in FIG. 3 overcomes the disadvantage of not being able to precisely control the introduction of treatment fluids. The system of FIG. 3, however, does suffer from one particular disadvantage in that the metering valve assembly is part of the production tube and, therefore, if the metering valve mechanism were needed to be removed in order to be repaired, it would be necessary to extract the whole production tube from the well. Such an operation would be extremely expensive in terms of both operating costs and production delays. A further disadvantage associated with the system shown in FIG. 3 and disclosed in the '985 patent is that the system can only be easily implemented in conjunction with tubing type subsurface pumps. An insert type pump cannot be effectively used due to the fact that it could not avoid the establishment of hydrostatic pressures against the oil reservoir which, as noted above with regard to FIG. 1, produces the negative effect of diminished efficiency of oil production. It is beneficial and advantageous to employ insert type pumps because they can readily be installed and removed from the well without having to extract the production tube from the well.
Accordingly, it is a principal object of the present invention to provide a system for improving the recovery of crude oil from a well which is capable of introducing precise quantities of treatment fluid to the pumping chamber of a subsurface oil pump.
It is a particular object of the present invention to provide a system as set forth above wherein a metering valve for controlling the introduction of treatment fluid into the pumping chamber is associated with the subsurface oil pump thereby allowing the pumping metering valve to be removed from the production tube as a unit.
It is still a further object of the present invention to provide a system as set forth above wherein the production tube is provided with a seating nipple for sealingly receiving a metering valve assembly which is adapted to receive subsurface oil pumps of both the barrel insert and barrel tubing type.
Further objects and advantages of the present invention will become more apparent from the following detailed description.